Piston assembly for human-powered vehicle

ABSTRACT

A piston assembly is provided for a human-powered vehicle. The piston assembly includes a main body, a primary seal and a secondary seal. The main body is configured to be movable from a rest position to an actuated position along an actuation direction in a cylinder bore. The primary seal includes a primary seal body arranged on the main body, the primary seal body being made of the first seal material. The secondary seal includes a secondary seal body arranged on the main body at upstream of the primary seal with respect to the actuation direction. The secondary seal body is made of a second seal material that is more elastic than the first seal material.

BACKGROUND Technical Field

This disclosure generally relates to a piston assembly. Morespecifically, the present disclosure relates to a piston assembly for ahuman powered vehicle.

Background Information

Human-powered vehicles (e.g., bicycles) are sometimes provided withhydraulic devices. Examples of some hydraulic devices include ahydraulic operating device and a hydraulic operated device. A hydraulicoperating device is operated by a user to hydraulically operate thehydraulic operated device. For example, in a hydraulic braking system, ahydraulic brake operating device is fluidly connected to a hydraulicbrake device such that a user operates a brake lever of a hydraulicbrake operating device to actuate a hydraulic brake device to engage abrake rotor or a rim of a wheel. One example of hydraulic braking systemis disclosed in U.S. Pat. No. 9,874,238 B2.

SUMMARY

Generally, the present disclosure is directed to various features of apiston assembly for a human-powered vehicle such as a bicycle. The term“human-powered vehicle” as used herein refers to a vehicle that can bedriven by at least human driving force, but does not include a vehicleusing only a driving power other than human power. In particular, avehicle solely using an internal combustion engine as a driving power isnot included in the human-powered vehicle. The human-powered vehicle isgenerally assumed to be a compact, light vehicle that does not require alicense for driving on a public road. The number of wheels on thehuman-powered vehicle is not limited. The human-powered vehicleincludes, for example, a monocycle and a vehicle having three or morewheels. The human-powered vehicle includes, for example, various typesof bicycles such as a mountain bike, a road bike, a city bike, a cargobike, and a recumbent bike, and an electric assist bicycle (E-bike).

In view of the state of the known technology and in accordance with afirst aspect of the present disclosure, a piston assembly for ahuman-powered vehicle. The piston assembly basically comprises a mainbody, a primary seal and a secondary seal. The main body is configuredto be movable from a rest position to an actuated position along anactuation direction in a cylinder bore. The primary seal includes aprimary seal body arranged on the main body. The primary seal body ismade of the first seal material. The secondary seal includes a secondaryseal body arranged on the main body at upstream of the primary seal withrespect to the actuation direction. The secondary seal body is made of asecond seal material that is more elastic than the first seal material.

With the piston assembly according to the first aspect, it is possibleto provide a piston assembly that has an improved sliding with respectto the cylinder bore.

In accordance with a second aspect of the present disclosure, the pistonassembly according to the first aspect is configured so that the firstseal material includes a resin material.

With the piston assembly according to the second aspect, it is possibleto provide a piston assembly that has an improved sliding with respectto the cylinder bore by using a resin material as a first seal materialof the primary seal.

In accordance with a third aspect of the present disclosure, the pistonassembly according to the second aspect is configured so that the firstseal material includes one of polytetrafluoroethylene and polyethylene.

With the piston assembly according to the third aspect, it is possibleto inexpensively manufacture the primary seal.

In accordance with a fourth aspect of the present disclosure, the pistonassembly according to the second or third aspect is configured so thatthe first seal material includes polyimide-filledpolytetrafluoroethylene.

With the piston assembly according to the fourth aspect, it is furtherpossible to inexpensively manufacture the primary seal.

In accordance with a fifth aspect of the present disclosure, the pistonassembly according to any one of the first to fourth aspects isconfigured so that the second seal material includes a rubber material.

With the piston assembly according to the fifth aspect, it is possibleto inexpensively improve the seal between the main body and the cylinderbore.

In accordance with a sixth aspect of the present disclosure, the pistonassembly according to any one of the first to fifth aspects isconfigured so that the primary seal body includes a primary lip portionconfigured to be in contact with the cylinder bore in an arranged statewhere the piston assembly is arranged in the cylinder bore, and theprimary seal further includes a biasing part that is configured tooutwardly bias the primary lip portion of the primary seal body in thearranged state.

With the piston assembly according to the sixth aspect, it is possibleto reliably and firmly maintain contact of the secondary seal with thecylinder bore while the piston assembly moves axially in the cylinderbore.

In accordance with a seventh aspect of the present disclosure, thepiston assembly according to the sixth aspect is configured so that thebiasing part is a coil spring.

With the piston assembly according to the seventh aspect, it is possibleto easily apply a radially directed force to maintain the primary sealin contact with the cylinder bore.

In accordance with an eighth aspect of the present disclosure, thepiston assembly according to any one of the first to seventh aspects isconfigured so that the secondary seal body includes a secondly lipportion that is configured to be in contact with the cylinder bore in anarranged state where the piston assembly is arranged in the cylinderbore.

With the piston assembly according to the eighth aspect, it is possibleto maintain reliably contact of the secondary seal with the cylinderbore while the piston assembly moves axially in the cylinder bore.

In accordance with a ninth aspect of the present disclosure, the pistonassembly according to any one of the first to eighth aspects isconfigured so that the main body includes a first part and a secondpart. The first part is configured to limit movement of the primary sealwith respect to the main body in a return direction opposite to theactuation direction. The second part is configured to limit movement ofthe primary seal with respect to the main body in the actuationdirection.

With the piston assembly according to the ninth aspect, it is possibleto properly maintain the position of the primary seal with respect tothe main body in an axial direction of the movement of the pistonassembly in the cylinder bore.

In accordance with a tenth aspect of the present disclosure, the pistonassembly according to the ninth aspect is configured so that the secondpart is detachably and reattachably attached to the first part.

With the piston assembly according to the tenth aspect, it is possibleto easily install the primary seal on the main body.

In accordance with an eleventh aspect of the present disclosure, thepiston assembly according to the tenth aspect is configured so that thefirst part has a first axial abutment surface facing the primary seal,the second part has a second axial abutment surface facing the primaryseal, and at least one of the first part and the second part includes aconnecting portion disposed in an axial position between the first axialabutment surface and the second axial abutment surface.

With the piston assembly according to the eleventh aspect, it ispossible to properly maintain the position of the primary seal withrespect to the main body in an axial direction of the movement of thepiston assembly in the cylinder bore.

In accordance with a twelfth aspect of the present disclosure, thepiston assembly according to the eleventh aspect is configured so thatthe connecting portion is integral with the second part, and the secondpart is threadedly engaged to the first part.

With the piston assembly according to the twelfth aspect, it is possibleto easily manufacture the first part and the second part, and easilyattach the first part and the second part together.

In accordance with a thirteenth aspect of the present disclosure, thepiston assembly according to the eleventh aspect is configured so thatthe connecting portion is integral with the first part, and the secondpart is threadedly engaged to the connecting portion of the first part.

With the piston assembly according to the thirteenth aspect, it ispossible to easily manufacture the first part and the second part, andeasily attach the first part and the second part together.

In accordance with a fourteenth aspect of the present disclosure, thepiston assembly according to any one of the ninth to thirteenth aspectsis configured so that the first part is made of a first material, andthe second part is made of a second material that is different from thefirst material.

With the piston assembly according to the fourteenth aspect, it ispossible to optimize the materials for assembly.

In accordance with a fifteenth aspect of the present disclosure, thepiston assembly according to any one of the ninth to fourteenth aspectsis configured so that the main body further includes a third partcoupled to the first part, the third part is configured to limitmovement of the secondary seal with respect to the main body in thereturn direction, and the first part is configured to limit movement ofthe secondary seal with respect to the main body in the actuationdirection.

With the piston assembly according to the fifteenth aspect, it ispossible to easily install the secondary seal.

In accordance with a sixteenth aspect of the present disclosure, thepiston assembly according to the fifteenth aspect is configured so thatthe first part is made of a first material, the second part is made of asecond material that is different from the first material, and the thirdpart is made of the third material that is different from the secondmaterial.

With the piston assembly according to the sixteenth aspect, it ispossible to optimize the materials for assembly.

In accordance with a seventeenth aspect of the present disclosure, thepiston assembly according to the fourteenth or sixteenth aspect isconfigured so that the first material is a resin material, and thesecond material is a metallic material.

With the piston assembly according to the seventeenth aspect, it ispossible to improve sliding of the main body with respect to thecylinder bore by using a resin material for the first part that maycontact the cylinder bore while using a metallic material for the secondpart to secure the first part and the second part together.

In accordance with an eighteenth aspect of the present disclosure, thepiston assembly according to the sixteenth or seventeenth aspect isconfigured so that the third material is same as the first material.

With the piston assembly according to the eighteenth aspect, it ispossible to lower manufacturing costs.

In accordance with a nineteenth aspect of the present disclosure, thepiston assembly according to any one of the fifteenth to eighteenthaspects is configured so that the third part is press-fitted to thefirst part.

With the piston assembly according to the nineteenth aspect, it ispossible to inexpensively couple the third part to the first part.

Also, other objects, features, aspects and advantages of the disclosedpiston assembly will become apparent to those skilled in the art fromthe following detailed description, which, taken in conjunction with theannexed drawings, discloses preferred embodiments of the pistonassembly.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the attached drawings which form a part of thisoriginal disclosure:

FIG. 1 is a top perspective view of a portion of a handlebar of ahuman-powered vehicle that is equipped with a hydraulic operating devicehaving a piston assembly (not shown in this Figure) in accordance with afirst embodiment;

FIG. 2 is a top plan view of the portion of the handlebar and thehydraulic operating device illustrated in FIG. 1;

FIG. 3 is a partial cross-sectional view of the hydraulic operatingdevice illustrated in FIGS. 1 and 2 with the piston assembly shown in afull view and in which the cross section is taken along section planethat is perpendicular to and passes through a cylinder axis of acylinder bore of the base of the hydraulic operating device;

FIG. 4 is a partial cross-sectional view, similar to FIG. 3, of thehydraulic operating device illustrated in FIGS. 1 to 3, but in which theoperating member has been moved to an actuated position;

FIG. 5 is a first end perspective view of the piston assemblyillustrated in FIGS. 3 and 4 in accordance with a first embodiment;

FIG. 6 is a second end perspective view of the piston assemblyillustrated in FIGS. 3 to 5;

FIG. 7 is a longitudinal cross-sectional view of the piston assemblyillustrated in FIGS. 3 to 6;

FIG. 8 is a first exploded perspective view of the piston assemblyillustrated in FIGS. 3 to 7;

FIG. 9 is a second exploded perspective view of the piston assemblyillustrated in FIGS. 3 to 8;

FIG. 10 is a longitudinal cross-sectional view of a piston assembly inaccordance with a second embodiment for use in the hydraulic operatingdevice illustrated in FIG. 1;

FIG. 11 is a partial longitudinal cross-sectional view of a portion ofthe piston assembly illustrated in FIG. 1 but with a first modifiedprimary seal;

FIG. 12 is a partial longitudinal cross-sectional view of a portion ofthe piston assembly illustrated in FIG. 1 but with a second modifiedprimary seal;

FIG. 13 is a partial longitudinal cross-sectional view of a portion ofthe piston assembly illustrated in FIG. 1 but with a third modificationof the primary seal as seen along section line 13-13 of FIG. 14;

FIG. 14 is a transverse cross-sectional view of the piston assemblyillustrated in FIG. 13 as seen along section line 14-14 of FIG. 13; and

FIG. 15 is a partial longitudinal cross-sectional view of a portion ofthe piston assembly illustrated in FIG. 1 but with a fourth modificationof the primary seal.

DETAILED DESCRIPTION OF EMBODIMENTS

Selected embodiments will now be explained with reference to thedrawings. It will be apparent to those skilled in the human-poweredvehicle field (e.g., the bicycle field) from this disclosure that thefollowing descriptions of the embodiments are provided for illustrationonly and not for the purpose of limiting the invention as defined by theappended claims and their equivalents.

Referring initially to FIG. 1, an operating device 10 is provided for ahuman-powered vehicle V (only a handlebar H is shown) in accordance witha first illustrative embodiment. Here, in the illustrated embodiments,the operating device 10 is a hydraulic operating device that is providedfor the human-powered vehicle V (e.g., a bicycle). The operating device10 is mounted to the handlebar H of the human-powered vehicle V. Here,the human-powered vehicle V is preferably a bicycle. Thus, the operatingdevice 10 is a bicycle hydraulic brake operating device. Hereinafter,the operating device 10 is consistently referred as the hydraulicoperating device 10.

The hydraulic operating device 10 is fluidly connected to a hydraulicoperated device (not shown) by a hydraulic hose 12. As illustrated inFIGS. 1 to 4, the hydraulic operating device 10 is a right-hand sidehydraulic brake actuating device that is operated by the rider's righthand from a rest or non-operated position (FIGS. 1 to 3) to an operatedposition (FIG. 4) for actuating the hydraulic operated device such as adisc brake caliper or a rim brake caliper. It will be apparent to thoseskilled in the human-powered vehicle field that the configuration of thehydraulic operating device 10 can be adapted to a left-hand sidehydraulic brake actuating device that is operated by the rider's lefthand. Also, the hydraulic operating device 10 can be used with othervehicle components other than a brake caliper.

The hydraulic operating device 10 basically comprises a base 14, anoperating member 16 and a handlebar mounting structure 18. Here, thehandlebar mounting structure 18 is coupled to the base 14. The base 14is a rigid member that is typically made of a metallic material. Thebase 14 includes a handlebar contact portion 20. The handlebar contactportion 20 is configured to contact the handlebar H in a mounted statein which the base 14 is mounted to the handlebar H by the handlebarmounting structure 18. It will be apparent from this disclosure that thehandlebar mounting structure 18 is not limited to the illustratedembodiment, and that other types of handlebar mounting structures can beused.

Here, the operating member 16 includes a user operating lever 22 and atorque input member 24. The user operating lever 22 is pivotally coupledto the base 14 by a pivot pin 26 about a pivot axis P1 between a restposition (see FIGS. 1 to 3) and an operated position (FIG. 4). The useroperating lever 22 is a rigid member that is typically made of ametallic material or a hard resin material. The torque input member 24is also pivotally coupled to the base 14 by the pivot pin 26 about thepivot axis P1. The torque input member 24 is a rigid member that istypically made of a metallic material or a hard resin material.

As mentioned above, in the illustrated embodiments, the hydraulicoperating device 10 is a bicycle hydraulic operating device. In such acase, as seen in FIGS. 3 and 4, the base 14 includes a cylinder bore 14a that defines the cylinder axis A1. Here, as seen in FIGS. 1 and 2, thehydraulic operating device 10 includes a hydraulic reservoir 28 that isfilled with a fluid such as mineral oil. The hydraulic reservoir 28 isin fluid communication with the cylinder bore 14 a in a state where theoperating lever 22 is in the rest position. Since hydraulic reservoirsare well known, the hydraulic reservoir 28 will not be discussed orillustrated in detail herein.

The hydraulic operating device 10 further comprises a piston assembly 30that is movably provided in the cylinder bore 14 a. Thus, the pistonassembly 30 is provided for the human-powered vehicle V. The pistonassembly 30 is inserted into the cylinder bore 14 a from an open end 14b of the cylinder bore 14 a. The base 14 has a fluid port 14 c that isin fluid communication with the cylinder bore 14 a. The hydraulic hose12 is fluidly connected to the fluid port 14 c by a hose connector 12 aof the hydraulic hose 12 and a banjo bolt 32 (see FIG. 1).

A biasing element 34 is disposed in the cylinder bore 14 a, and biasesthe piston assembly 30 to a non-actuated (rest or non-operated)position. Here, the biasing element 34 is a coil compression spring thatbiases the piston assembly 30 to the non-actuated position. The biasingelement 34 also biases the operating member 16 to its rest position(i.e., no external force applied to the operating member 16). Thus, thepiston assembly 30 compresses the biasing element 34 as the pistonassembly 30 moves in the cylinder bore 14 a in response to an operationof the user operating lever 22 of the operating member 16.

The piston assembly 30 is operatively coupled to the operating member 16to move the piston assembly 30 within the cylinder bore 14 a in responseto operation of the operating member 16. Namely, as seen in FIG. 4, thepiston assembly 30 is coupled to the operating member 16 to be pushed inresponse to a pivotal movement of the operating member 16 from the restposition to the operated position. The piston assembly 30 moves linearlyalong the cylinder axis A1 within the cylinder bore 14 a in response tooperation of the operating member 16. Here, the hydraulic operatingdevice 10 further comprises a torque transmission mechanism 40 thatoperatively connects the piston assembly 30 and the torque input member24 of the operating member 16. In this way, by a user operating the useroperating lever 22, the torque transmission mechanism 40 pushes thepiston assembly 30 in the cylinder bore 14 a.

Here, the torque transmission mechanism 40 includes a torquetransmission member 42, a connection rod 44 and a pair of cam guides 46(only one shown). The torque transmission member 42 is pivotally coupledto the base 14 by a pivot pin 48 about a pivot axis P2. The torquetransmission member 42 is a rigid member that is typically made of ametallic material or a hard resin material. As the torque input member24 of the operating member 16 is pivoted by a user pivoting the useroperating lever 22, the torque input member 24 pivots the torquetransmission member 42, which in turn pushes the connection rod 44. As aresult of the connection rod 44 being pushed by the torque transmissionmember 42, the piston assembly 30 is pushed in the cylinder bore 14 a bythe connection rod 44. Thus, the connection rod 44 operatively connectsthe piston assembly 30 to the torque transmission member 42.

Here, the connection rod 44 basically includes a shaft 44 a, a yoke 44b, a roller 44 c and a support pin 44 d. The shaft 44 a has one endoperatively connected to the piston assembly 30 and a second end fixedto the yoke 44 b. The yoke 44 b rotatably supports the roller 44 c viathe support pin 44 d. The roller 44 c is preferably rotatably supportedon the support pin 44 d by a bearing (not shown). The ends of thesupport pin 44 d are located in the cam guides 46 for controlling themovement of the connection rod 44 with respect to the base 14.

Specifically, the cam guides 46 are mounted to the base 14 on oppositesides of the connection rod 44. Thus, the cam guides 46 support the endsof the support pin 44 d of the connection rod 44 to the base 14. The camguides 46 are shaped to control movement of the piston assembly 30 inresponse to the movement of the user operating lever 22 of the operatingmember 16. Namely, each of the cam guides 46 has a profiled cam surfacethat controls the movement of the piston assembly 30 with respect to themovement of the operating member 16.

Turning now to FIGS. 5 to 9, the piston assembly 30 will now bediscussed in more detail. The piston assembly 30 comprises a main body50 and a primary seal 52. In this illustrated embodiment, the pistonassembly 30 further comprises a secondary seal 54. However, it will beapparent from this disclosure that the secondary seal 54 can be omittedas need and/or desired. The primary seal 52 and the secondary seal 54are provided on the main body 50 such that the primary seal 52 and thesecondary seal 54 slidably contact the cylinder bore 14 a. Thus, theprimary seal 52 and the secondary seal 54 are in sealing contact withthe cylinder bore 14 a and the main body 50.

As seen in FIGS. 3 and 4, the main body 50 is configured to be movablefrom a rest position (FIG. 3) to an actuated position (FIG. 4) along anactuation direction D1 in the cylinder bore 14 a. In other words, themain body 50 of the piston assembly 30 moves against the urging force ofthe biasing element 34 in the actuation direction D1 in the cylinderbore 14 a in response to actuation of the user operating lever 22 of theoperating member 16. Once the user operating lever 22 of the operatingmember 16 is released, the main body 50 of the piston assembly 30 movesin the cylinder bore 14 a under the urging force of the biasing element34 in a return direction D2 that is opposite the actuation direction D1.Thus, the main body 50 has an upstream end 50 a that is located nearestto the open end 14 b of the cylinder bore 14 a, and a downstream end 50b that is located nearest to the fluid port 14 c of the base 14. Inother words, the term “upstream” and the term “downstream” as usedherein refer to locations with respect to the actuation direction D1.

Referring again to FIGS. 5 to 9, the main body 50 includes a first part56 and a second part 58. In this illustrated embodiment, the main body50 further includes a third part 60 coupled to the first part 56. In thecase in which the secondary seal 54 is omitted, then the third part 60can also be omitted. Here, the second part 58 is detachably andreattachably attached to the first part 56. However, it will be apparentfrom this disclosure that the first part 56 and the second part 58 canbe permanently fix together if needed and/or desired. Here, the thirdpart 60 is a separate part from the first part 56. The third part 60 isattached to the first part 56 at the opposite end from the second part58. For example, the third part 60 is press-fitted to the first part 56.However, it will be apparent from this disclosure that the third part 60can be detachably and reattachably attached to the first part 56 in thesame manner that the second part 58 is coupled to the first part 56.

The first part 56 is at least partly arranged upstream of the primaryseal 52 with respect to the actuation direction D1. The second part 58is coupled to the first part 56 to be at least partly arrangeddownstream of the primary seal 52 with respect to the actuationdirection D1. Thus, the primary seal 52 is at least partly arrangedbetween the first part 56 and the second part 58. The third part 60 iscoupled to the first part 56 to be at least partly arranged upstream ofthe secondary seal 54 with respect to the actuation direction D1. Thus,the secondary seal 54 is at least partly arranged between the first part56 and the third part 60. In this illustrated embodiment, the third part60 has a spherical concave portion at the upstream end 50 a and a ballportion of the connection rod 44 is connected to the spherical concaveportion of the third part 60. Namely, the main body 50 is connected tothe connection rod 44 with a ball joint.

The first part 56 has an outermost diameter that is equal to or slightlysmaller than an inner diameter of the cylinder bore 14 a so that thefirst part 56 can be slidably in contact with the cylinder bore 14 a. Onthe other hand, the second part 58 has an outermost diameter that issmaller than the outermost diameter of the first part 56 so that thesecond part 58 is spaced radially inward of the cylinder bore 14 a.Preferably, the third part 60 has an outermost diameter that is equal toor slightly smaller than an inner diameter of the cylinder bore 14 a sothat the third part 60 can be slidably in contact with the cylinder bore14 a.

In the illustrated embodiment, the first part 56 is made of a firstmaterial. The second part 58 is made of a second material that isdifferent from the first material. Preferably, the first material of thefirst part 56 is a resin material. The second material of the secondpart 58 is a metallic material. The resin material of the first part 56has a lower coefficient of friction than the metallic material of thesecond part 58. In this way, the first part 56 can slide easily on theinner surface of the cylinder bore 14 a. The third part 60 is made of athird material that is different from the second material. Preferably,the third material of the third part 60 is a resin material. Morepreferably, as in the illustrated embodiment, the third material of thethird part 60 is same as the first material of the first part 56. Inthis way, the third part 60 can slide easily on the inner surface of thecylinder bore 14 a.

Referring to FIG. 7, the first part 56 is configured to limit movementof the primary seal 52 with respect to the main body 50 in the returndirection D2. In particular, the first part 56 has a first axialabutment surface 61 facing the primary seal 52. The second part 58 isconfigured to limit movement of the primary seal 52 with respect to themain body 50 in the actuation direction D1. In particular, the secondpart 58 has a second axial abutment surface 62 facing the primary seal52. In this way, the movement of the primary seal 52 with respect to themain body 50 is limited in the axial direction between the first part 56and the second part 58 when the piston assembly 30 moves in the cylinderbore 14 a. At least one of the first part 56 and the second part 58includes a support or connecting portion 63 for supporting the primaryseal 52. Here, in the embodiment of FIGS. 5 to 9, the second part 58includes the support portion 63 that supports the primary seal 52. Thesupport portion 63 is disposed in an axial position between the firstaxial abutment surface 61 and the second axial abutment surface 62. Thesupport portion 63 is integral with the second part 58. Thus, here, thesecond part 58 supports the primary seal 52.

The first part 56 is configured to limit movement of the secondary seal54 with respect to the main body 50 in the actuation direction D1. Inparticular, the first part 56 has a third axial abutment surface 64facing the secondary seal 54. The third part 60 is configured to limitmovement of the secondary seal 54 with respect to the main body 50 inthe return direction D2. In particular, the third part 60 has a fourthaxial abutment surface 65 facing the secondary seal 54. In this way, themovement of the secondary seal 54 with respect to the main body 50 islimited in the axial direction between the first part 56 and the thirdpart 60 when the piston assembly 30 moves in the cylinder bore 14 a. Atleast one of the first part 56 and the third part 60 includes a supportor connecting portion 64 supporting the secondary seal 54. Here, in theembodiment of FIGS. 5 to 9, the third part 60 includes the supportportion 64 that supports the primary seal 52. Preferably, the supportportion 64 is integral with the third part 60. Thus, here, the thirdpart 60 supports the secondary seal 54.

As mentioned above, the second part 58 is detachably and reattachablyattached to the first part 56 to be at least partly arranged downstreamof the primary seal 52 with respect to the actuation direction D1. Inparticular, the second part 58 is inserted into the first part 56 to beat least partly arranged downstream of the primary seal 52 with respectto the actuation direction D1. Here, the second part 58 is threadedlyengaged to the first part 56. More specifically, the second part 58includes a tapping screw portion 66 that is configured to be threadedlyengaged to the first part 56. Here, the first part 56 includes a blindbore 68 that is tapped by the tapping screw portion 66 as the secondpart 58 is connected to the first part 56. Thus, the blind bore 68becomes a threaded bore after the second part 58 is connected to thefirst part 56. Alternatively, the blind bore 68 can be pre-threaded.Also, alternatively, the second part 58 and/or the third part 60 can beattached to the first part 56 in other manners (e.g., adhesion, welding,and so on) after arranging the primary seal 52 and/or the secondary seal54 in their appropriate position(s).

As mentioned above, the third part 60 is attached to the first part 56to be at least partly arranged upstream of the secondary seal 54 withrespect to the actuation direction D1. In particular, the third part 60is inserted into the first part 56 to be at least partly arrangedupstream of the secondary seal 54 with respect to the actuationdirection D1. Here, the third part 60 is press-fitted to the first part56. More specifically, the third part 60 includes a pressing portion 70that is configured to be press-fitted into a blind bore 71 of the firstpart 56. Here, the blind bore 71 has a plurality of longitudinal ribsthat are plastically deformed to create an interference fit.

The primary seal 52 includes a primary seal body 80 arranged on the mainbody 50. The primary seal body 80 is made of the first seal material.Here, the primary seal body 80 is made of a resin material. Thus, thefirst seal material includes a resin material. Preferably, the firstseal material (the resin material) includes one ofpolytetrafluoroethylene and polyethylene. More preferably, the firstseal material includes polyimide-filled polytetrafluoroethylene.

The primary seal body 80 is an O-ring that has uniform cross sectionalprofile. The primary seal body 80 includes a primary lip portion 80 aconfigured to be in contact with the cylinder bore 14 a in an arrangedstate where the piston assembly 30 is arranged in the cylinder bore 14a. The primary seal body 80 further includes a center opening 80 bconfigured to snugly contact the support portion 63 of the second part58. The primary seal 52 further includes a biasing part 82 that isconfigured to outwardly bias the primary lip portion 80 a of the primaryseal body 80 in the arranged state. Here, the biasing part 82 is a coilspring. However, it will be apparent from this disclosure that thebiasing part 82 is not limited to a coil spring. For example, thebiasing part 82 can be an annular elastomeric O-ring or an annularcantilever or V-spring having a V-shaped cross section, or any othersuitable member or members that can be used to apply a radially urgingforce to the primary lip portion 80 a of the primary seal body 80. Thus,preferably, the primary seal 52 is a spring-energized seal as thebiasing part 82 is included.

The secondary seal 54 is arranged on the main body 50 upstream of theprimary seal 52 with respect to the actuation direction D1. Namely, thesecondary seal 54 includes a secondary seal body 54 a arranged on themain body 50 upstream of the primary seal 52 with respect to theactuation direction D1. The secondary seal body 54 a is an O-ring thathas uniform cross sectional profile. The secondary seal body 54 a ismade of a second seal material that is more elastic than the first sealmaterial. The secondary seal body 54 a includes a secondly lip portion54 b that is configured to be in contact with the cylinder bore 14 a inan arranged state where the piston assembly 30 is arranged in thecylinder bore 14 a. Preferably, the second seal material of thesecondary seal body 54 a includes a rubber material.

Referring now to FIG. 10, a piston assembly 130 in accordance with asecond embodiment will now be explained. Basically, the piston assembly130 is used in place of the piston assembly 30 in the hydraulicoperating device 10. In view of the similarity between the first andsecond embodiments, the parts of the second embodiment that areidentical to the parts of the first embodiment will be given the samereference numerals as the parts of the first embodiment. Moreover, thedescriptions of the parts of the second embodiment that are identical tothe parts of the first embodiment may be omitted for the sake ofbrevity.

The piston assembly 130 comprises a main body 150, the primary seal 52of the first embodiment and the secondary seal 54 of the firstembodiment. The main body 130 includes a first part 156, a second part158 and the third part 60 of the first embodiment. As mentioned above,the secondary seal 54 and the third part 60 can be omitted as neededand/or desired. Here, the third part 60 is coupled to the first part 156and supports the secondary seal 54 in the same manner as in the pistonassembly 30 of the first embodiment. However, in the second embodiment,the primary seal 52 is supported on the first part 156, and theconnection between the first part 156 and the second part 158 has beenmodified.

Here, in the second embodiment, the first part 156 includes a support orconnecting portion 163 for supporting the primary seal 52. The supportportion 163 is integral with the first part 156. Also, here, in thesecond embodiment, the second part 158 is threadedly engaged to thesupport or connecting portion 163 of the first part 156. Morespecifically, the second part 158 includes a tapping screw portion 166that is configured to be threadedly engaged to the first part 156. Here,the first part 156 includes a blind bore 168 that is tapped by thetapping screw portion 166 when the second part 158 is connected to thefirst part 156. Thus, the blind bore 168 becomes a threaded bore afterthe second part 158 is connected to the first part 156. Alternatively,the blind bore 168 can be pre-threaded. Also, alternatively, the secondpart 158 and/or the third part 60 can be attached to the first part 156in other manners (e.g., adhesion, welding, and so on) after arrangingthe primary seal 52 and/or the secondary seal 54 in their appropriateposition(s).

Referring now to FIG. 11, a first modified primary seal 252 is providedbetween the first part 56 of the main body 50 and the second part 58 ofthe main body 50. The first modified primary seal 252 includes theprimary seal body 80, discussed above, and a biasing part 282. Here, thebiasing part 282 is an annular cantilever spring having a V-shaped orU-shaped cross section. The biasing part 282 can be made of a suitablemetallic material, a resin material or an elastomeric material.

Referring now to FIG. 12, a second modified primary seal 352 is providedbetween the first part 56 of the main body 50 and the second part 58 ofthe main body 50. The second modified primary seal 352 includes theprimary seal body 80, discussed above, and a biasing part 382. Here, thebiasing part 382 is an annular elastomeric spring that fills the annularspace inside the primary seal body 80. However, the biasing part 382 canbe an O-ring with a circular cross section. The biasing part 382 isshown as being removable but could be embedded or bonded to the primaryseal body 80.

Referring now to FIGS. 13 and 14, a third modified primary seal 452 isprovided between the first part 56 of the main body 50 and the secondpart 58 of the main body 50. The third modified primary seal 452includes the primary seal body 80, discussed above, and a biasing part482. Here, the biasing part 482 is an annular elastomeric spring with aplurality of recesses. These recesses can be through holes and/or haveother shapes. In the illustrated embodiment, the biasing part 482 fillsthe annular space inside the primary seal body 80. However, the biasingpart 482 can be an O-ring with a circular cross section. The biasingpart 482 is preferably removable but could be embedded or bonded to theprimary seal body 80.

Referring now to FIG. 15, a fourth modified primary seal 552 is providedbetween the first part 56 of the main body 50 and the second part 58 ofthe main body 50. The fourth modified primary seal 552 includes theprimary seal body 80, discussed above, and a biasing part 582. Here, thebiasing part 582 is an annular cantilever spring having a V-shaped orU-shaped cross section with two resin layers. However, the biasing part582 can have more than two layers as needed and/or desired. As shown,the layers of the biasing part 582 can have different hardnesses asneeded and/or desired. The biasing part 582 is shown as being removablebut could be embedded or bonded to the primary seal body 80. Thehardness of resins of the biasing part 582 can be harder or softer thanthe primary seal body 80 as needed and/or desired.

In understanding the scope of the present invention, the term“comprising” and its derivatives, as used herein, are intended to beopen ended terms that specify the presence of the stated features,elements, components, groups, integers, and/or steps, but do not excludethe presence of other unstated features, elements, components, groups,integers and/or steps. The foregoing also applies to words havingsimilar meanings such as the terms, “including”, “having” and theirderivatives. Also, the terms “part,” “section,” “portion,” “member” or“element” when used in the singular can have the dual meaning of asingle part or a plurality of parts unless otherwise stated.

As used herein, the following directional terms “frame facing side”,“non-frame facing side”, “forward”, “rearward”, “front”, “rear”, “up”,“down”, “above”, “below”, “upward”, “downward”, “top”, “bottom”, “side”,“vertical”, “horizontal”, “perpendicular” and “transverse” as well asany other similar directional terms refer to those directions of ahuman-powered vehicle (e.g., the bicycle) in an upright, riding positionand equipped with the piston assembly. Accordingly, these directionalterms, as utilized to describe the piston assembly should be interpretedrelative to a human-powered vehicle (e.g., the bicycle) in an uprightriding position on a horizontal surface and that is equipped with thepiston assembly. The terms “left” and “right” are used to indicate the“right” when referencing from the right side as viewed from the rear ofthe human-powered vehicle (e.g., the bicycle), and the “left” whenreferencing from the left side as viewed from the rear of thehuman-powered vehicle (e.g., the bicycle).

The phrase “at least one of” as used in this disclosure means “one ormore” of a desired choice. For one example, the phrase “at least one of”as used in this disclosure means “only one single choice” or “both oftwo choices” if the number of its choices is two. For another example,the phrase “at least one of” as used in this disclosure means “only onesingle choice” or “any combination of equal to or more than two choices”if the number of its choices is equal to or more than three.

Also, it will be understood that although the terms “first” and “second”may be used herein to describe various components, these componentsshould not be limited by these terms. These terms are only used todistinguish one component from another. Thus, for example, a firstcomponent discussed above could be termed a second component and viceversa without departing from the teachings of the present invention.

The term “attached” or “attaching”, as used herein, encompassesconfigurations in which an element is directly secured to anotherelement by affixing the element directly to the other element;configurations in which the element is indirectly secured to the otherelement by affixing the element to the intermediate member(s) which inturn are affixed to the other element; and configurations in which oneelement is integral with another element, i.e. one element isessentially part of the other element. This definition also applies towords of similar meaning, for example, “joined”, “connected”, “coupled”,“mounted”, “bonded”, “fixed” and their derivatives. Finally, terms ofdegree such as “substantially”, “about” and “approximately” as usedherein mean an amount of deviation of the modified term such that theend result is not significantly changed.

While only selected embodiments have been chosen to illustrate thepresent invention, it will be apparent to those skilled in the art fromthis disclosure that various changes and modifications can be madeherein without departing from the scope of the invention as defined inthe appended claims. For example, unless specifically stated otherwise,the size, shape, location or orientation of the various components canbe changed as needed and/or desired so long as the changes do notsubstantially affect their intended function. Unless specifically statedotherwise, components that are shown directly connected or contactingeach other can have intermediate structures disposed between them solong as the changes do not substantially affect their intended function.The functions of one element can be performed by two, and vice versaunless specifically stated otherwise. The structures and functions ofone embodiment can be adopted in another embodiment. It is not necessaryfor all advantages to be present in a particular embodiment at the sametime. Every feature which is unique from the prior art, alone or incombination with other features, also should be considered a separatedescription of further inventions by the applicant, including thestructural and/or functional concepts embodied by such feature(s). Thus,the foregoing descriptions of the embodiments according to the presentinvention are provided for illustration only, and not for the purpose oflimiting the invention as defined by the appended claims and theirequivalents.

What is claimed is:
 1. A piston assembly for a human-powered vehicle, the piston assembly comprising: a main body configured to be movable from a rest position to an actuated position along an actuation direction in a cylinder bore; a primary seal including a primary seal body arranged on the main body, the primary seal body being made of the first seal material; and a secondary seal including a secondary seal body arranged on the main body at upstream of the primary seal with respect to the actuation direction, the secondary seal body being made of a second seal material that is more elastic than the first seal material.
 2. The piston assembly according to claim 1, wherein the first seal material includes a resin material.
 3. The piston assembly according to claim 2, wherein the first seal material includes one of polytetrafluoroethylene and polyethylene.
 4. The piston assembly according to claim 2, wherein the first seal material includes polyimide-filled polytetrafluoroethylene.
 5. The piston assembly according to claim 1, wherein the second seal material includes a rubber material.
 6. The piston assembly according to claim 1, wherein the primary seal body includes a primary lip portion configured to be in contact with the cylinder bore in an arranged state where the piston assembly is arranged in the cylinder bore, and the primary seal further includes a biasing part that is configured to outwardly bias the primary lip portion of the primary seal body in the arranged state.
 7. The piston assembly according to claim 6, wherein the biasing part is a coil spring.
 8. The piston assembly according to claim 1, wherein the secondary seal body includes a secondly lip portion that is configured to be in contact with the cylinder bore in an arranged state where the piston assembly is arranged in the cylinder bore.
 9. The piston assembly according to claim 1, wherein the main body includes a first part that is configured to limit movement of the primary seal with respect to the main body in a return direction opposite to the actuation direction, and a second part that is configured to limit movement of the primary seal with respect to the main body in the actuation direction.
 10. The piston assembly according to claim 9, wherein the second part is detachably and reattachably attached to the first part.
 11. The piston assembly according to claim 10, wherein the first part has a first axial abutment surface facing the primary seal, the second part has a second axial abutment surface facing the primary seal, and at least one of the first part and the second part includes a connecting portion disposed in an axial position between the first axial abutment surface and the second axial abutment surface.
 12. The piston assembly according to claim 11, wherein the connecting portion is integral with the second part, and the second part is threadedly engaged to the first part.
 13. The piston assembly according to claim 11, wherein the connecting portion is integral with the first part, and the second part is threadedly engaged to the connecting portion of the first part.
 14. The piston assembly according to claim 9, wherein the first part is made of a first material, and the second part is made of a second material that is different from the first material.
 15. The piston assembly according to claim 9, wherein the main body further includes a third part coupled to the first part, the third part is configured to limit movement of the secondary seal with respect to the main body in the return direction, and the first part is configured to limit movement of the secondary seal with respect to the main body in the actuation direction.
 16. The piston assembly according to claim 15, wherein the first part is made of a first material, the second part is made of a second material that is different from the first material, and the third part is made of the third material that is different from the second material.
 17. The piston assembly according to claim 16, wherein the first material is a resin material, and the second material is a metallic material.
 18. The piston assembly according to claim 16, wherein the third material is same as the first material.
 19. The piston assembly according to claim 15, wherein the third part is press-fitted to the first part. 